Lead-activated barium silicate phosphors are described in U.S. Pat. Nos. 2,499,307, 2,597,631, 3,043,781, 3,984,346, 3,987,331, 4,147,816, and 4,691,140.
The lead source used in prior art methods of making lead-activated barium silicate phosphors is generally lead oxide. Because lead oxide has a relatively high vapor pressure, it partially volatilizes at the temperature at which the barium silicate phosphor is formed. As a result, approximately two-thirds of the initial amount of lead provided as lead oxide is lost to the environment before it can be integrated into the phosphor. Substantial excesses of lead oxide must therefore be used to provide sufficient lead in the phosphor.